The present invention relates generally to the field of heat sinks and more specifically to the field of heat sinks configured to maximize thermal conduction with heat generating devices that may not be co-planar with the heat sink.
Modern electronics have benefited from the ability to fabricate devices on a smaller and smaller scale. As the ability to shrink devices has improved, so has their performance. Unfortunately, this improvement in performance is accompanied by an increase in power as well as power density in devices. In order to maintain the reliability of these devices, the industry must find new methods to remove this heat efficiently.
By definition, heat sinking means that one attaches a cooling device to a heat-generating component and thereby removes the heat to some cooling medium, such as air or water. Unfortunately, one of the major problems in joining two devices to transfer heat through a common surface is that a thermal interface is created at the junction. This thermal interface is characterized by a thermal contact impedance. Thermal contact impedance is a function of contact pressure, surface finish, and gap size.
As the power density of electronic devices increases, heat transfer from the heat generating devices to the surrounding environment becomes more and more critical to the proper operation of the devices. Many current electronic devices incorporate heat sink fins to dissipate heat to the surrounding air moving over the fins. These heat sinks are thermally connected to the electronic devices by a variety of techniques. Some devices use a thermally conductive paste in an attempt to lower the contact resistance. Others may use solder between the two elements both for mechanical strength and thermal conductance. However, these two solutions require additional cost and process steps that would not be necessary except for presence of the contact resistance.
Many present electronic modules include a plurality of heat-generating electronic devices on a single substrate. Often these devices to not have a co-planer upper surface which would allow a single heat sink to be thermally coupled to the plurality of devices. Thermal paste and other thermally conductive materials may be used to fill any gaps between the heat-generating electronic devices and the single heat sink, however large gaps, caused by tolerance stack-up issues between the heat-generating devices, are often not capable of being filled by a paste. Thermal gap pads are capable of filling gaps on the order of 20 to 200 mils, however, they have relatively low thermal conductivity, and may not be usable with high performance devices that generate large amounts of heat. In such cases, multiple heat sinks may be used, however, this adds cost and reduces the efficiency of the heat dissipation.
A heat sink is constructed including at least one thermally conductive pedestal, allowing configuration of the heat sink to make contact with a plurality of heat-generating electronic devices where the devices may not be co-planar due to tolerance stack-up. The pedestals may be raised and lowered and tilted as needed to match the heights and tilts of the electronic devices. Within the heat sink is a cavity above the pedestal that may be filled with a thermally conductive material, such as solder, or a thermally conductive liquid, during construction to create a low thermal resistance contact between the pedestal and the heat sink fins. Also, thermally conductive material, such as thermal paste or a thermal pad, may be used between the heat generating device and the pedestal to create a low thermal resistance contact.